Donor-Acceptor Polymer Networks from Triarylborane and Thiophene Building Blocks for Photocatalytic Hydrogen Evolution from Aqueous Solution

Photocatalytic water-splitting provides a carbon-neutral alternative to energy-intensive electrolysis to store solar energy in the form of hydrogen. Microporous polymer networks are an intriguing platform for the design of increasingly more performant photocatalysts due to their chemical modularity and band-gap tuning potential. Their efficacy depends on the efficient separation of photoexcited electron-hole pairs. Conventionally, this is achieved by deposition of expensive platinum as co-catalyst. More recently, however, it was recognized that efficiency of polymer photocatalysts can be improved by incorporation of donor-acceptor motifs into their backbones. While electron donors are plentiful, there is little variety in electron acceptor motifs. We synthesised a series of microporous donor-acceptor networks that contain electron-deficient triarylborane moieties with the unique electronic properties of tricoordinate boron as an electron acceptor. Under sacrificial conditions, these polymers feature hydrogen evolution rates of up to 113.9 mmol h-1 g-1 that decrease only marginally under omission of platinum co-catalyst. This work outlines a clear synthetic strategy towards truly noble-metal-free photocatalysts.

Effective Photocatalytic Hydrogen Evolution Using Covalent Triazine Framework-Derived Carbon Nitride Nanofiber Containing Carbon Vacancies for Visible-Light-Driven

In this study, a novel fibrous carbon nitride (FCN) was prepared from laminated covalent triazine framework (CTF) via pyrolysis, using functionalized 2,5-thiophenedicarboxylic acid and melamine as the precursors. A carbon vacancy was produced by two-step calcination in argon and air atmospheres. These carbon vacancies further exposed the edges and diffusion channels of the FCN nanofibers, which accelerated photogenerated charge transfer and provided more active sites. The FCN was characterized using various techniques and used for H2 evolution under visible-light irradiation. The as-synthesized FCN exhibited excellent stability, and its photocatalytic activity for H2 evolution under visible-light irradiation was 66 times higher than that of bare C3N4 (BCN), attaining a maximum H2 evolution rate of 102.63 μmol in 6 h. The FCN remained stable following visible-light irradiation at the end of 10 cycles. The FCN benefited from the absorption of solar energy and a large number of active sites. These advantages facilitated the efficient separation of photoexcited electron-hole pairs to hinder charge recombination. This work generates new insights into the preparation of highly effective FCN photocatalysts that may be put to various applications, especially in the fields of energy and environment.

Anatomy of a Natural Sunlight Driven CdS/CoTiO3/ZnO Ternary Photocatalyst for Efficient Optical Properties and Removal of Reactive Orange 30

ZnO as a promising photocatalyst has gained much attention for the removal of organic pollutants from water. However, the main drawbacks of the relatively low photocatalytic activity and high recombination rate of photoexcited electron-hole pairs restrict its potential applications. Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis because the difference in the band positions makes the potential gradient at the composite boundary. In this work, binary CdS/ZnO and CoTiO3/ZnO are first prepared by dispersion method and then decorated with ZnO particles to construct CdS/CoTiO3/ZnO ternary composites. For this reason, the CdS/CoTiO3/ZnO ternary composites was effectively designed and analyzed for the crystalline structure, light absorption, photoexcitation behavior and surface morphological properties by X-ray diffraction, diffuse reflectance UV/visible absorption spectroscopy, photoluminescence spectroscopy and scanning electron micrograph respectively. The photocatalytic activity was examined by degradation of the dye solution spectrophotometrically. The results of photocatalytic degradation indicated that the CdS/CoTiO3/ZnO ternary composites are much higher than those of bare CdS, CoTiO3, ZnO and any binary composites such as CoTiO3/ZnO and ZnO/CdS. The enhanced activity could be attributed to the drop electron transfer from CdS to ZnO to CoTiO3 through the interfacial potential gradient in the ternary hybrid conduction bands. The enhanced electron transfer of CdS/CoTiO3/ZnO ternary composites was also applicable to degrade other reactive dyes.

Hydrothermal fabrication and characterization of novel CeO2/PbWO4 nanocomposite for enhanced visible-light photocatalytic performance

In this revision, a series of novel visible-light-driven (VLD) CeO2/PbWO4 nanocomposites (NCs) were effectively fabricated by facile hydrothermal preparation way. The UV–Vis absorption spectra exposed that CeO2 NPs prolonged the adsorption edge of the CeO2/PbWO4 composite to the extensive visible region, which allied to decreases of the bandgap. As-prepared CeO2/PbWO4 NCs revealed superior photocatalytic action under visible-light and could degrade the Methylene Blue (MB) dye solution in 140 min. The photodegradation efficacy of CeO2/PbWO4 NCs was improved catalytic activity, which is around 1.45 and 2.7 times that of CeO2 and PbWO4 nanoparticles (NPs) individually. Besides, the CeO2/PbWO4 catalysts display notable stability and reusability performance in four succeeding cycles. The development in the photocatalytic enactment of combined CeO2/PbWO4 nanocomposite could be recognized not only to the sturdy visible-light absorption responses and separating the photoexcited electron–hole pairs. Also, the plausibly systematic illumination of charge transference and exploitation of reactive species for superior photocatalytic action in visible-light have been discussed. It is projected that the CeO2/PbWO4 NCs could be used as effective photocatalysts for promising applications for environmental wastewater refinement.

CoB/C3N4 photocatalyst for rapid hydrogen evolution from hydrolysis of sodium borohydride under light irradiation

For practical application of sodium borohydride (NaBH[Formula: see text] hydrolysis to generate hydrogen, metallic catalysts with low cost but excellent activity are highly desired. However, it remains a big challenge to further improve the activity of non-noble metal catalysts. In this work, photocatalysis technology was successfully introduced to enhance the catalyst activity for NaBH4 hydrolysis. By means of conventional impregnation-reduction method, CoB nanocatalyst was evenly deposited on graphitic carbon nitride surface, resulting in a Schottky-type photocatalyst (CoB/CN). As expected, hydrogen generation rate was greatly boosted owing to light irradiation. According to the results of capture experiments, photoexcited electron from g-C3N4 could enrich the electron density of CoB surface, which leads to the improvement of catalyst activity. Additionally, the light irradiation facilitates the remarkable decrease of apparent activation energy. Compared with some reported noble metal catalysts, the CoB/CN presents higher activity, especially under light irradiation.